• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1561-1575
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• 2002

A reduced-order linear feedback controller, which is used to control the linear disturbance in two-dimensional plane Poiseuille flow, is applied to a boundary layer flow for stability control. Using model reduction and linear-quadratic-Gaussian/loop-transfer-recovery control synthesis, a distributed controller is designed from the linearized two-dimensional Navier-Stokes equations. This reduced-order controller, requiring only the wall-shear information, is shown to effectively suppress the linear disturbance in boundary layer flow under the uncertainty of Reynolds number. The controller also suppresses the nonlinear disturbance in the boundary layer flow, which would lead to unstable flow regime without control. The flow is relaminarized in the long run. Other effects of the controller on the flow are also discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1809-1818
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• 1997

Mathematical models of industrial robots or manipulators are highly nonlinear equations with nonlinear coupling between the variables of motion. As the working speed has been fast, the effects of nonlinear terms have become serious. So the control algorithm based on approximately linearized equation looses the efficiency. In order to design the control law for the nonlinear models, Hunt-Su's nonlinear transformation method and Marino's feedback equivalence condition are used with linear quadratic regulator(LQR) theory in this study. Nonlinear terms of the system are eliminated and coupled terms are decoupled by this feedback law. This method is applied to a 3-D.O.F. vertical articulated manipulator by both experiments and simulations and compared with PID control which is widely used in the industry.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.4
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• pp.352-365
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• 2001

Two-level factorial designs are popular in industry due to their simplicity, efficiency, graphical interpretation, and flexibility in sequential experimentation. However, experimenters are often frustrated when they have factors with more than two levels. There have been some works on design of experiments with two- and four-level factors, which mostly deal with qualitative four-level factors. This paper discusses differences between qualitative and quantitative four-level factors. Optimal designs are provided for some designs with four-level quantitative and two-level factors.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.3
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• pp.3872-3877
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• 1975

This study was conducted to examine the effects of the change of cap hole diameter and pressure on the travelling distance and the sprayed particle size for the medium range nozzle. The results of this study are summarized as follows; 1) The effective travelling distance was about from 1 meter to 8 meters and centro-position of the travelling distance was about 3 or 5 meters. 2) Main effect of change of cap hole diameter for the travelling distance was a slight convex quadratic curve. 3) Main effect of change of pressure increased linearly, its increasing rate about 1.6 was large. 4) Sizes of sprayed particles were less than 250${\mu}$ generally and the sizes decreased according to the increasing of travelling distance. 5) Changes of diameter of sprayed particles by cap hole diameter increased in accordance with increasing of cap hole diameter. 6) Changes of diameter of sprayed particles by the groove depth of swirl plate was very slight.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.266-268
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• 2006

In this paper, we design a Linear Quadratic Gaussian(LQG) controller for active suspensions. We can improve the inherent suspension problem, trade-off between the ride quality and the suspension travel by selecting appropriate weights in the LQ-objective function. Using an optimization-algorithm, Evolution Strategy(ES), we find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle's state variables. The frequencies and proper control gains are used for the neural network data. During a vehicle running, the trained on-line neural network is activated and provides the proper gains for non-trained frequencies.

• Journal of Veterinary Clinics
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• v.21 no.3
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• pp.286-290
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• 2004

Cytogenetic and hematological analysis was performed in peripheral blood of pig in the vicinity of Yeonggwang nuclear power station and control area. The frequency of micronuclei (MN) in peripheral blood lymphocytes from pig was used as a biomarker of radiobiological effects resulting from exposure to environmental radiation. An estimated dose of radiation was calculated by a best fitting linear-quadratic model based on the radiation-induced MN formation from the swine lymphocytes exposed in vitro to radiation over the range from 0 Gy to 4 Gy. MN rates in lymphocytes of pig from Yeonggwang nuclear power station and control area were 10.60/1,000 and 11.10/1,000, respectively. There were no significant differences in MN frequencies and hematological values in pig between Yeonggwang and control area. The study indicates that the MN assay in lymphocyte of pig is a rapid, sensitive and accurate method that can be used to monitor a large population exposed to radiation.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.329-353
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• 2014

Increasing usage of tank cars and their intrinsic instability due to sloshing of contents have caused growing maintenance costs as well as more frequent hazards and defects like derailment and fatigue of bogies and axels. Therefore, varieties of passive solutions have been represented to improve dynamical parameters. In this task, assuming 22 degrees of freedom, dynamic analysis of partially filled tank car traveling on a curved track is investigated. In order to consider stochastic geometry of track; irregularities have been derived randomly by Mont Carlo method. More over the fluid tank model with 1 degree of freedom is also presented by equivalent mechanical approach in terms of pendulum. An active suspension system for described car is designed by using linear quadratic optimal control theory to decrease destructive effects of fluid sloshing. Eventually, the performance of the active suspension system has been compared with that of the passive one and a study is carried out on how active suspension may affect the dynamical parameters such as displacements and Nadal's derailment index.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1530-1533
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• 2005

In this paper, we design a Linear Quadratic Gaussian controller for the active suspension. We can improve the inherent suspension problem, trade-off between the ride quality and the suspension travel by selecting appropriate weights in the LQ-objective function. Because any definite rules for selecting weights do not exist, we use an optimization-algorithm, Evolution Strategy (ES) to find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle's state variables. The frequencies and proper control gains are used for the neural network data. During a vehicle running, the trained on-line neural network is activated and provides the proper gains for non-trained frequencies. For the full-state feedback control, Kalman filter observes the full states and Fourier transform is used to detect the frequency of the road.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1118-1124
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• 2014

This paper proposes a novel controller design scheme for multimachine power systems based on the explorized policy iteration. Power systems have several uncertainties on system dynamics due to the various effects of interconnections between generators. To solve this problem, the proposed method solves the LQR (Linear Quadratic Regulation) problem of isolated subsystems without the knowledge of a system matrix and the interconnection parameters of multimachine power systems. By selecting the proper performance indices, it guarantees the stability and convergence of the LQ optimal control. To implement the proposed scheme, the least squares based online method is also investigated in terms of PE (Persistency of Excitation), interconnection parameters and exploration signals. Finally, the performance and effectiveness of the proposed algorithm are demonstrated by numerical simulations of three-machine power systems with governor controllers.

• Journal of Magnetics
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• v.17 no.4
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• pp.275-279
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• 2012

The linear actuator has the inherent drawback of air gap variation because its linear motion is usually guided by the springs, which destabilizes the dynamic performance. In order to design the linear actuator to be insensitive to air gap, this paper describes the robust design of the air compressor driving linear actuator using Taguchi method. The orthogonal arrays are constructed with selected control factors and noise factor for minimum experiment. The control factors are thickness of inner magnet, height of upper yoke, thickness of outer magnet and thickness of lower yoke while noise factor is airgap. The finite element analysis using commercial electromagnetic analysis program "MAXWELL" are performed instead of experiment. ANOVA are performed to investigate the effects of design factors. In result, the optimal robust linear actuator which is insensitive to air gap variation is designed.